A class of mental retardation, due to the inherited disorder of sphingolipid metabolism is collectively called sphingolipidoses. The overall objective of this work is to understand the biochemical etiology as well as chemical pathology of sphingolipidoses. We propose to isolate various glycosidases pertinent to the sphingolipidoses and to use these glycosidases to study the catabolism of various glycosphingolipids such as GM1-ganglioside, GM2-ganglioside and ceramide trihexoside, etc. Our objectives and long term goals are: a) isolation of homogeneous glycosidases from various sources, especially those enzymes capable of hydrolyzing the glycosphingolipids accumulated in sphingolipid storage diseases. b) characterization of the physical, chemical and biological properties of the enzymes isolated. c) to use these enzymes to study the normal degradation of glycosphingolipids. d) to continue our effort on the isolation and characterization of the protein activator(s) which stimulate the enzymic hydrolysis of glycosphingolipids. e) to use glycosidases as a tool for the structural analysis of glycoconjugates.